The performances of a large and complex code are affected by a number of factors: hardware[1], compilation [2], mathematical libraries[3], parallelism[4], obvious[5] and less obvious[6] conflicts for resources, phase of the moon[7] and alignment of planets[8]...
Paolo [1] Not only CPU speed but also speed of memory access, size of cache,...As a rule: the cheaper the hardware, the slower the speed [2] Can make a sizable difference, but, as Lorenzo says, not a factor 10 [3] These, especially FFTs and linear algebra, can also make a sizable difference [4] There are many ways to use a given number of processors; just increasing their number is not always the right thing to do [5] Some other process running on the same processor [6] Memory access conflicts, unwanted OpenMP threads, ... [7-8] By far the most important factors:-) Many years ago, I watched in disbelief the same run taking 27 s in one case, 30 in another, reproducibly. The difference? a single print statement, executed once. On Sat, Jan 23, 2021 at 10:22 PM Robert Stanton <stan...@clarkson.edu> wrote: > Dear all, > > I am able to successfully install parallel QE and get everything to > run smoothly, however after testing against an install on an externally > maintained cluster I'm finding my speed to be slower by a factor of 5-10x > when keeping the system, core number, QE version, etc. the same. > > I'm not sure the degree to which this could be a hardware discrepancy > (Xeon Silvers vs new EPYCs), v.s. how much could be a sub-optimal > compilation of QE. The slower QE install is being done with blas/lapack > 3.8.0 and openmpi 1.10.7. I'm just curious if there is anything very > clearly not ideal about this environment, or if it is likely something I'll > just need to troubleshoot with smaller settings? Thanks so much in advance > for any insights you can provide! > > Regards, > Robert Stanton > Graduate Student > Clarkson University > > _______________________________________________ > Quantum ESPRESSO is supported by MaX (www.max-centre.eu) > users mailing list users@lists.quantum-espresso.org > https://lists.quantum-espresso.org/mailman/listinfo/users -- Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche, Univ. Udine, via delle Scienze 206, 33100 Udine, Italy Phone +39-0432-558216, fax +39-0432-558222
_______________________________________________ Quantum ESPRESSO is supported by MaX (www.max-centre.eu) users mailing list users@lists.quantum-espresso.org https://lists.quantum-espresso.org/mailman/listinfo/users